Most engines combust a mixture of air and fuel to generate a mechanical, hydraulic, or electrical power output. In order to improve combustion of the air/fuel mixture and protect components of the engine from damaging extremes, temperatures of the engine and air drawn into the engine for combustion should be tightly controlled. For this reason, combustion engines are generally fluidly connected to several different liquid-to-air and/or air-to air heat exchangers to cool both liquids and gases circulated throughout the engine. An engine-driven fan is disposed either in front of the exchanger to blow air across the exchanger and the associated engine, or between the exchanger and engine to suck air past the engine and blow air past the exchanger. The airflow from the fan may function to remove heat from the heat exchanger and the engine.
Although this cooling arrangement may improve combustion in extreme conditions and thereby help to reduce a likelihood of engine damage caused by high temperatures, it may suffer from inefficiencies. In particular, when a fan is mechanically coupled to an engine, the speed of the fan is dependent on engine speed, which is generally the result of a desired machine travel speed and/or an actual loading condition. Accordingly, conventional fans are only able to rotate at a speed that is some fixed ratio of a travel or load-governed engine speed. In some situations, this speed may be sufficient to provide a desired amount of cooling. In other situations, however, this fixed ratio may result in too little or too much cooling, which may cause reduced engine efficiencies.
One way to improve cooling-related engine efficiencies is described in U.S. Pat. No. 5,747,883 (the '883 patent) issued to Hammer et al. on May 5, 1998. The '883 patent discloses an engine-driven fan that circulates air through a powertrain compartment and radiator. Specifically, the '883 patent describes an engine that is drivingly connected with an output shaft on which is disposed a bevel gear. The bevel gear is connected to a variable drive mechanism, such as pairs of slipping clutches, belt drives, or a hydrostatic transmission. The bevel gear is also connected through a pair of spur gears to a modulating shaft having a hub with a plurality of integral fan blades. The modulating shaft and integral fan blades are driven by the engine via the bevel and spur gears, with a speed of the shaft and blades being varied relative to engine speed by the variable drive mechanism.
Although perhaps an improvement over fixed ratio fan systems, the cooling system of the '883 patent may still be less than optimal. In particular, the added components of the variable drive mechanism that are required to provide for decoupling of engine speed and fan speed may be complex, reduce reliability, and increase system costs.
The control system of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.